Cryo-EM characterization of the anydromuropeptide permease AmpG central to bacterial fitness and β-lactam antibiotic resistance.

Bacteria invest significant resources into the continuous creation and tailoring of their essential protective peptidoglycan (PG) cell wall. Several soluble PG biosynthesis products in the periplasm are transported to the cytosol for recycling, leading to enhanced bacterial fitness. GlcNAc-1,6-anhydroMurNAc and peptide variants are transported by the essential major facilitator superfamily importer AmpG in Gram-negative pathogens including Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa.

An alternative broad-specificity pathway for glycan breakdown in bacteria.

The vast majority of glycosidases characterized to date follow one of the variations of the 'Koshland' mechanisms to hydrolyse glycosidic bonds through substitution reactions. Here we describe a large-scale screen of a human gut microbiome metagenomic library using an assay that selectively identifies non-Koshland glycosidase activities. Using this, we identify a cluster of enzymes with extremely broad substrate specificities and thoroughly characterize these, mechanistically and structurally.

Cryo-EM analysis of TarL, a polymerase in wall teichoic acid biogenesis central to virulence and antibiotic resistance.

Wall teichoic acid (WTA), a covalent adduct of Gram-positive bacterial cell wall peptidoglycan, contributes directly to virulence and antibiotic resistance in pathogenic species. Polymerization of the WTA ribitol-phosphate chain is catalyzed by TarL, a member of the largely uncharacterized TagF-like family of membrane-associated enzymes. We report the cryo-electron microscopy structure of TarL, showing a tetramer that forms an extensive membrane-binding platform of monotopic helices.

"I Could Not Talk . . . She Did Everything . . . She's Now My Sister": People With Aphasia's Perspectives on Friends Who Stuck Around.

Purpose: Aphasia may decrease the capacity to develop and maintain friendships. The aim of this study was to better understand the perspectives of people with aphasia on why some friendship bonds remain strong and some do not. Furthermore, we wanted to explore how age and aphasia severity shape views on friendship.